It was probably back in 1997, though some think it might have been even earlier, when the Chestnut Hill Friends Meeting concluded that it had outgrown its space and that it was high time to erect a new building. But because it is not the Quaker way to rush into things, the group spent a few more years reflecting on whether it should buy land on Mermaid Lane for the new meetinghouse.

Even after the group sealed the deal in 2003, there was still plenty more talking and thinking and praying to be done about the undertaking. There was a "dialogue session" to articulate the group's "touchstone values," then, a year later, a workshop with a facilitator, and, finally - just to be certain - a retreat for members.

As agonizing as the process was, the result is a trim little design, faced in traditional Wissahickon schist, that will visibly reflect the ideals Quakers hold dear, from respect for the environment to plain old good neighborliness. And yet, in one crucial way, the $5.8 million project now under construction is also a frank acknowledgment of real-world conditions: To afford Philadelphia's first new Quaker meetinghouse in 80 years, the Chestnut Hill Friends felt their only option was to employ a nonunion contractor.

Four days before Christmas, the Friends' world was rocked by the sort of violence they have devoted their lives to stamping out.

Vandals with an acetylene torch crept onto the project's muddy construction site in the middle of the night. Working out of view in the meetinghouse's freshly cemented basement, they sliced off dozens of bolts securing the bare steel columns and set fire to the building crane, causing $500,000 in damage.

Police detectives deemed the attack arson because of a series of confrontational visits from union officials days before the incident. They say the torch could only have been operated by a trained professional, and believe it was almost certainly the work of disgruntled union members. The city has assigned extra investigators to the case and is working with federal forensic experts to track down the vandals, said Michael Resnick, the city's public safety commissioner.

It sounds like something out of the '50s movie On the Waterfront, not modern-day Philadelphia.

In many ways, the city's building sites are still run like those fictional dockyards. Trade unions dictate hiring at virtually all large construction projects in the city. Their dominance has had the virtue of ensuring that members receive good salaries and generous benefits, on par with those in New York. But it has also made construction exceptionally expensive here. Those high costs, real estate experts like Kevin C. Gillen at Econsult argue, have been a drag on the city's revival.

Through all the changes Philadelphia has undergone in the last decade - the surge in its downtown population, the blossoming of its inner-ring neighborhoods - the trade unions haven't budged on the cost issue. Cross them by hiring nonunion workers or demanding more efficient work rules, and you can expect a giant inflatable rat at your door - or worse. The Post brothers, who are renovating a former factory into apartments at 12th and Wood Streets, learned the hard way in the spring when union protesters laid siege to their construction site, blocking deliveries for five months.

The Quakers' decision to go nonunion may be a sign of a broader shift in attitudes. The group, known for its commitment to social justice, chose contractor E. Allen Reeves of Abington after conducting a blind review of bids. Reeves' price was 23 percent lower than the nearest union bidder, the group says.

It was not an easy decision, acknowledged Meg Mitchell, clerk of the meeting, the closest thing the non-hierarchial group has to a spokesperson. But after assuring themselves that Reeves was paying fair wages and that his company had maintained an excellent safety record, she said, the Chestnut Hill Friends dropped any lingering reservations.

Despite their frugality, the Quakers wanted to spend money where it counted, on serving their members and the public. The meetinghouse design, by Bryn Mawr's James Bradberry Architects, features two gable roof structures - the kind a child might draw - that sit perpendicularly on the wooded site, linked by a glass vestibule.

The slightly lower one contains a traditional Quaker meeting room; the taller structure houses offices, classrooms, and an event space and kitchen designed to double as emergency housing for homeless families. An elevator serves the basement, so the building is fully handicapped accessible. It was designed to be highly energy efficient.

The design also offers a gift to the wider community: an installation by the celebrated artist James Turrell. A retractable opening in the roof is intended to bathe the meeting room in a purple glow at dusk and dawn, creating a serene meditation space that will be open to everyone. The public artwork helped the Quakers win an $80,000 grant from the National Endowment for the Arts.

In the past, city trade unions would probably never have noticed a small, nonunion project like the Friends meetinghouse. Their focus was on maintaining a union presence at big-ticket, high-rise, and institutional projects. But as growing costs make it harder to pull off such projects, Philadelphia has become a city of smaller, low-budget buildings.

The future is likely to favor a nimble and efficient workforce at construction sites. With their high level of skill and good safety record, the trade unions should have a lot to offer. But they won't be able to compete under the old terms. Like everyone else, they will need to adapt to the demands of the modern world.

The use of brute force isn't just a throwback to the past. It's the sort of behavior that diminishes the unions' valid attempts to remain relevant.